The squiggly line above the letter "N"

That little squiggly line is actually called a tilde. There are a few ways to type one. First, if you're typing in Word, you can look through their symbols list until you find the letter you want. Alternatively, you can hold down the alt key and type 0209 using your number pad to make Ñ or type 0241 to make Ñ. I just spent some time trying to figure out how to do this on a laptop and for me, I had to use the function key to turn on the number pad first (then remember to turn it back off when I was done!). On a Mac, you have to hold down the Opt key and press the letter n (or so I've heard - I can't exactly test it out on my computer).

Jess pointed out some good ways to produce the tilde with the letter n. I want to mention that this letter is most commonly recognized in the Spanish alphabet and writing. If you need to write using Spanish letters, you can activate your keyboard's international settings and then use the apostrophe key with the letter to get the letter Ñ and other letters too, in case you can't remember the code numbers.